1. Field of the Invention
The present invention relates to a DC noise absorbing device for preventing surges and regulating voltages and, particularly, to a DC noise absorbing device connected in parallel with and between a DC supply and a DC load, for absorbing surges generated by switching the DC supply and the DC load, voltage fluctuations caused by load variation, serial surges rebounding from the DC load, and noises produced by external interference so that a stable operation and a promoted efficiency of the DC system can be achieved.
2. Descriptions of the Related Art
As the continuous innovation of technology, various novel electronic products have been developed out for employment. The electronic products are mostly driven by DC (direct-current) power and, therefore, the best effectiveness thereof may be achieved with a stable DC power. In the DC power, there can be voltage surges, ripples and other noises generated due to frequently switching, too numerous loads connected in series and temporal variation of the load, and even generated when using DC power to drive a motor. These surges, ripples and noises can communicate through power supply wires, resulting in interference among the loads and making destruction. Analysis with the Fourier series shows that the DC power has a series of harmonics accompanying the DC component. In particular, the surge is composed of harmonics with frequencies distributed in the full band. Different loads under the same DC power may undergo different currents and may have different impedances; thus, the load may resonate or interfere with certain harmonics, exhibiting decreased effectiveness. For example, in the mobile's electric system, which uses a single DC power, continuous surges generated when driving the motor and switching relays with large current passing, as well as the different impedances of different loads, can make the control signals interfered and, thus, influence the entire effectiveness of the mobile.
Moreover, a surge is a signal associated with voltage abruptly rising or dropping during an extreme short period. The extreme large voltage generated relates to an extreme strong electric field; that is,
                    Δ        ⁢                                  ⁢        v            =              -                              ∫            i            f                    ⁢                                                    E                ρ                            ·                                                          ⁢                              ⅆ                                  r                  ρ                                                      ⁢                                                  ⁢                          (                              in                ⁢                                                                  ⁢                scalar                ⁢                                                                  ⁢                form                            )                                            ,    or            =                  -                  ∇          v                    ⁢                          ⁢                        (                      in            ⁢                                                  ⁢            vector            ⁢                                                  ⁢            form                    )                .            In general, an electronic device such as a transistor is made of semiconductor, which might have been doped with donors or acceptors as being P-typed or N-typed semiconductor, respectively. Easily, the strong field with the large voltage for the surge can break the covalent bonds of the semiconductor, leading to lattice breakdown. In a long term, the semiconductor will be damaged ultimately; the relevant electronic equipment will be damaged also. In the replacement of electronic equipment or parts, and in the consequent manufacture of electronic components, pollution is inevitable due to the waste and carbon dioxide produced. If such destructive noises can be absorbed or removed, the electronic component will have a much longer life and a more effective period; in this way, environmental protection will be promoted since the pollution will be inhibited.
The conventional voltage regulating device is characterized by that several capacitors differing in capacity are used so as to achieve voltage regulation. The major disadvantages are as follows.
An instantaneous high voltage can be generated by switching a power supply or a load. Since a DC capacitor has polarity, instantaneously loading a half-maximum voltage can cause the capacitor to be biased reversibly; consequently, the capacitor will be damaged or lead a shorten life.
Since each load has its characteristic impedance and is associated with a characteristic bandwidth, loads connected to a DC power supply tend to be influenced by various harmonics. For the low-frequency noises, a typical voltage regulating device has neither a function nor bandwidth design to make them decay.
In the disclosure of TW Patent No. I244445 and U.S. Pat. No. 7,301,747, which were issued to one of the present inventors, the claimed noise absorbing capacitors together with relevant components do not have a protective design in which diodes, Zener diodes and DIACs (diode alternate current switches) having different switching voltages are orderly connected in parallel and are disposed in a staircase form; they do not have a function of low-frequency noise decay, either. Therefore, the shorten life and increased rate of damage are possible.
Since the convention has such drawbacks as described above, it is hardly a good one. An improvement is required urgently.
In view of the above disadvantages derived from the conventional DC power supplies and DC loads, the present inventors, through a long-term study and practice, have set about the work of improvement and innovation that provides the present DC noise absorbing device for preventing surges and regulating voltages.